Priming mixture



50 rel.

Patented Jan. 31, 1933 JAMES E. BURNS, OF BEIDGEPORT, CONNECTICUT, ASSIGNOR TO REMINGTON ARMS I I COMPANY, INC., A CORPORATION OF DELAWARE PRIMING MIXTURE No Drawing.

'19 laid aside, in the course of a few days the surface of the barrel becomes corroded by substances which form underneath the oil and the formation of which cannot be prevented by an oil film. It is at the present time well understood that such after corrosion is caused by the combustion residues of a single universally used ingredient of the ammunition priming mixture.

With the advent of modern smokeless and semi-smokeless powders, it became necessary to greatly increase the heat and pressure generated upon the explosion of the priming mixture, thus necessitating a very powerful and dependable oxidizing agent. P0-

tassium chlorate has been quite universally "used for this purpose. The combustion of this substance, however, leaves a residue of very hygroscopic potassium chloride, which substance solidifies at a comparatively high temperature, and is driven by the high pressures prevailing Within the gun barrel into microscopic fissures and indentations in the surface from which it cannot be removed by mechanical swabbing, or by the universally used non-aqueous gun cleaning compositions.

Due to its hygroscopic character, the potassium chloride subsequently absorbs moisture and corrodes the gun barrel, even after it has been cleaned and oiled with great care.

Another very harmful effect which results from the use of ordinary ammunition, particularly ammunition which contains potassium chlorate either in the propellant powder or in the priming mixture, is the effect which for the purpose of this specification will be termed chemical erosion as distinguished from the mechanical erosion, or wear due to friction between the barrel surface and the metallic bullets which pass through the bar- Such chemical erosion consists of the Application filed March 23, 1927. Serial No. 177,848.

removal of particles of the barrel steel, probably by chemical combination with combustion residues of powder and priming mixture, and its occurrence in confined chiefly to an area adjacent to and extending a short distance rearwardly and a somewhat greater distance forwardly from the'cartridge shell mouth. It is at thispoint that the steel of the barrel and cartridge containing chamber is exposed to the action of the combustion residues under the highest pressure at the highest temperature, under which conditions the combustion residues are extraordinarily chemically active. number of ordinary cartridges have been fired show a distinct enlargement of the bar- 'rel' and the chamber adjacent to the shell mouth.

duces an open gap in which the departing Such enlargement not only probullet is entirely free and unsupported and which it must cross before engaging rifiing of the barrel, but likewise leave the forward end of the shell or powder case unsupported so that said shell expands into contact with the enlarged chamber on the firing of the cartridge, and its extraction from the chamher is rendered extremely diflicult.

WVhile in general any acid residues probably produce both chemical erosion and after corrosion, the residue of potassium chlorate is chiefly responsible for chemical erosion just as it is for, after corrosion. This residue, potassium chloride, at the high temperature prevailing in the gun barrel is probably partly dissociated and in a very chemically "active state. The free chlorine attacks and combines with the steel of the barrel removing a small quantity of the steel with each shot fired. The accuracy of the,

gun is soon greatly impaired and the roughened surface remaining is particularly susceptible to rusting when the gun is not in use.

For these reasons, theneed for a priming composition which does not include potassium or other chlorate's has long been felt, and many other oxidizing agents have been proposed and tried.

The preparation of a priming composi tion, however, is a delicate and diflicult Barrels in which a large qualities.

undertaking, involving many problems beside the yielding of a non-corrosive residue. While the ingredients must be capable of reacting with extreme rapidity when struck a sharp blow, they must also remain uncombined in an intimate mixture for an indefinite time. They must also be incapable of reacting with the surface metal of their containers. They must likewise remain stable and active for an indefinite time under extreme conditions of temperature and humidity.

The difiiculty of securing satisfactory priming mixtures is further, augmented by differences in the character of the powder used for diiferent styles'of cartridges. A powder which is diflicultto ignite requires a primer acting with a force and intensity which is very undesirable for powder which is more easily ignited. have not possessed the flexibility necessary to readilv adapt them to different powders. The" performance of aimixture comprising certain ingredients has been practicallyinvariable, and in order to vary the intensity and duration of therflame or other characteristics of the action, it has been necessary to completely reorganize the mixture.

The present invention contemplates a priming mixture which is not only positive and certain in action, stable and entirely noncorrosive, but is likewise susceptible of simple and ready control of its combustion characteristics. 7

Generally stated, priming mixtures include three classes of ingredients a fuel to be burned with heat and flame, an oxidizer'to furnish oxygen for the combustion of the fuel, and a material which is exploded by the impact of the firing pin with suflicient heat and flame to start the reaction between the oxidizer and the fuel. Said explosive ingredient will be call-ed the initial explosive or combustion initiator. Prior to the present invention the most widely used combustion initiator was mercury fulminate, and this invention comprises the discovery of combustion initiators which may wholly or in part replacemercury fulminate. Allof the ingredients of the mixture however must be such that no residues remain which will react to corrode the bore. of a v gun barrel. For an igniter or initial explosive the normal lead salt of trinitroresorcine has been found to be desirable. This salt may be advantageously used in conjunction with mercury fulminate, a non-corrosive oxidizer such as barium nitrate, and a fuel, such as antimony sulphide. The resulting mixture is entirely non-corrosive, and different samples show very unusually uniform powder igniting The lead trinitroresorcinate appears to act as a combustion accelerator, or more generally stated, as a, combustion regulator. While Priming mixtures in the main, mixtures ofthis type containing lead trinitroresorcinate burn more rapidly and are more forceful in action than those which do not contain lead trinitroresorcinate, the uncertain and erratic action of the latter mixture with its occasional instances of extraordinary and unaccountably forceful action entirely disappears. tions of the mixture show very marked uniformity in' functioning, thus furnishing the quality of perfect dependability which is so desirable in these compositions. Moreover, the rate of combustion and the heat and foi'cefulness of the action are susceptible of ready control by simple variations inthe proportions of the ingredients, and thus the mixture is adaptable to the ignition of different types of propellant powder. For this purpose the proportions of the ingredients may be varied substantially as follows:

Mercury fulminate 10% to 40% Antimony sulphide 20% to 45% Barium nitrate 10% to 60% Lead trinitroresorcinate 5% to 35% tion of lead trinitroresorcinate is 2153 meters per seconch Further, lead trinitroresorcinate is about 5th as sensitive to friction and percussion as mercury fulminate. Hence it would seem that the replacement of. a part of the mercury fulminate of a'general mixture by lead trinitroresorcinate would both reduce the sensitiveness of the mixture and decrease its rate of combustion; yet exactly the reverse condition was found.

A possible explanation of the extraordinary efi'ect. of the presence of lead trinitroresorcinate in mercury fulminate priming mixture is as follows: 7 i r 1 It has been found that when a quantity of mercury fulminate less than th gram is exploded alone it does not acquire the velocity of detonation which is acquired when a larger quantity is exploded. The ignition of th of a gram of mercury fulminate on Difierent por- The accepted rate of more rapidly detonating explosive perforates the plate without shattering it. Now the quantity of mercury fulminate in an individual priming charge is substantially less than th gram. Hence when ignited alone its rate of detonation or combustion would be far less than that of a larger quantity. It is believed that when lead trinitroresorcinate is present the flame produced when the mercury fulminate begins to burn rapidly ignites the lead trinitroresorcinate and under the heat and pressure thus generated the detonation rate of the mercury fulminate is very greatly increased. Thus something approaching the normal detonation rate of mercury fulminate is utilized and the powder igniting action of the primer thereby greatly accelerated. ,The foregoing constitutes applicants best theoretical explanation of the extraordinary inter-action of mercury fulminate and lead trinitroresorcinate in priming compositions.

Other non-corrosive oxidizing salts, such as lead chromate, lead nitrate, and potassium nitrate and other fuels such as leador copper sulphocyanate may wholly or in part replace barium nitrate and antimony sulphide. However, these and other details of the invention as herein described, are to be regarded as illustrative rather than restrictive, the invention being susceptible of embodiment in many different compositions all falling within a broad interpretation of the appended claims:

In said claims the term oxidizing ingredient is to be understood as defining that part of a priming mixture having an oxidizing function, whether comprising one material or more than one. Similarly the terms fuel and fuel ingredient are to be understood as embracing that part of a mixture primarily intended to be burned by the oxygen of the oxidizing ingredient, Whether or not more than one distinct material is included therein.

What is claimed is:

l. A priming mixture for ammunition, comprising normal lead trinitroresorcinate, mercury fulminate and a non-corrosive oxidizing ingredient.

2. A priming mixture for ammunition, comprising normal lead trinitroresorcinate, mercury fulminate and a fuel.

3. A priming mixture for ammunition comprising normal lead trinitroresorcinate, mercury fulminate, barium nitrate and an antimony sulphide.

4. A priming mixture for ammunition comprising normal lead trinitroresorcinate, mercury fulminate, a non-corrosive oxidizing ingredient, and an antimony sulphide.

5. A priming mixture for ammunition comprising normal lead trinitroresoroinate, mercury fulminate and a non-corrosive oxidizing ingredient comprising at least one salt of the group consisting of barium nitrate, lead nitrate and lead chromate.

6. A priming mixture for ammunition comprising normal lead trinitroresorcinate, mercury fulminate, a non-corrosive oxidizing ingredient including at least one salt of the group consisting of barium nitrate, lead nitrate and lead chromate, and a fuel ingredient comprising at least one material from the group consisting of antimony sulphide, lead sulphocyanate and copper sulphocyanate.

T. A priming mixture for ammunition, comprising normal lead trinitroresorcinate, mercury fulminate, barium nitrate, a second non-corrosive oxidizer and a fuel ingredient.

8. A priming mixture for ammunition comprising normal lead trinitroresoroinate, mercury fulminate, a non-corrosive oxidizing ingredient including a lead salt, and a suitable fuel ingredient.

9. A priming mixture substantially as follows:

Mercury fulminate 10% to 40% Antimony sulphide 20% to 45% Barium nitrate 10% to 60% Lead trinitroresorcinate 5% to 35% In witness whereof I have signed my name hereto this 17th day of March, 1927.

JAMES E. BURNS. 

